The longitudinal variation of salinity and the maximum salinity intrusion length in an alluvial estuary are important environmental concerns for policy makers and managers since they influence water quality, water utilization and agricultural development in estuarine environments and the potential use of water resources in general. The supermoon total lunar eclipse is a rare event. According to NASA, they have only occurred 5 times in the 1900s – in 1910, 1928, 1946, 1964 and 1982. After the 28 September 2015 total lunar eclipse, a Super Blood Moon eclipse will not recur before 8 October 2033. In this paper, for the first time, the impact of the combination of a supermoon and a total lunar eclipse on the salinity intrusion along an estuary is studied. The 28 September 2015 supermoon total lunar eclipse is the focus of this study and the Sebou river estuary (Morocco) is used as an application area. The Sebou estuary is an area with high agricultural potential, is becoming one of the most important industrial zones in Morocco and it is experiencing a salt intrusion problem. Hydrodynamic equations for tidal wave propagation coupled with the Savenije theory and a numerical salinity transport model (HEC-RAS software "Hydrologic Engineering Center River Analysis System") are applied to study the impact of the supermoon total lunar eclipse on the salinity intrusion. Intensive salinity measurements during this extreme event were recorded along the Sebou estuary. Measurements showed a modification of the shape of axial salinity profiles and a notable water elevation rise, compared with normal situations. The two optimization parameters (Van der Burgh's and dispersion coefficients) of the analytical model are estimated based on the Levenberg–Marquardt's algorithm (i.e., solving nonlinear least-squares problems). The salinity transport model was calibrated and validated using field data. The results show that the two models described very well the salt intrusion during the supermoon total lunar eclipse day. A good fit between computed salinity and measurements is obtained, as verified by statistical performance tests. These two models can give a rapid assessment of salinity distribution and consequently help to ensure the safety of the water supply, even during such infrequent astronomical phenomenon.

Microplastics (MPs) are emerging contaminants and present risks to human and environmental health. Microplastic levels were examined in sediment and surface water samples at stations along the Sebou Estuary and Atlantic Coast of Morocco. The microplastic abundance, distribution, and characteristics were characterized. The microplastics were separated into fragments, fibers, films, and granules. The results at all stations showed that the microplastic abundance in water samples ranged from 10 to 168 particles/m³, whereas in the sediment samples, the levels were from 10 to 300 particles/kg. Stations adjacent to Kenitra City showed significantly high levels of microplastics (p < 0.001) compared with the Atlantic Coast, likely due to population density and human activity. The majority of the detected microplastics was from 0.1 to 0.5 mm, followed by 0.5 to 1 mm. The predominant shape in water and sediments were fragments. The results for the type, size, and color of the microplastics suggest the Sebou Estuary is a hotspot on the Atlantic Coast. The results of this study may contribute to increased awareness and better implementation of solid waste management plans, especially at Kenitra City, to protect the biologically diverse ecosystem of the Moroccan Estuary and Atlantic Coast.

Global climate change has resulted in a gradual sea-level rise. Sea-level rise can cause saline water to migrate upstream in estuaries and rivers, thereby threatening freshwater habitat and drinking water supplies. On the other hand, sea-level rise, resulting from thermal expansion of ocean waters and increased melting of glaciers and ice caps, is one of the most apparent and widespread consequences of climate change. This phenomenon has been taken into account in all the Assessment Reports published by the Intergovernmental Panel on Climate Change (IPCC). In this paper, salinity intrusion and intrusion length due to possible sea-level rise in the Sebou estuary (Morocco) was investigated. A one-dimensional hydrodynamic-salinity transport model was used for the simulation of the salinity intrusion and associated water quality, with observed field data being used for model calibration and validation. Additionally, the model validation process showed that the model results fit the observed data fairly well. A coupled gas-cycle/climate model was used to generate the climate change scenarios in the studied area that showed sea-level rises varying from 0.3 to 0.9 m for 2100. The models were then combined to assess the impact of future sea-level rise on the salinity distribution and intrusion length in the Sebou estuary. The response of salt intrusion length to changes in important dimensional parameters are presented, showing that the salinity intrusion length is inversely correlated with the river discharge, i.e., a high river discharge results in a reduced salt intrusion and vice versa, and directly with the sea-level rise. Additionally, the magnitude and frequency of the salinity standard violations at the two pump stations were predicted for 2100, showing that the salinity violations under climate change effects can increase to ∼45–48% of the times at these locations. Finally, the main objective of this simulation method is to accelerate and facilitate of systems' behavior learning in the current and future situation.

The present study analyzed the concentrations of four heavy metals iron (Fe), manganese (Mn), zinc (Zn), and lead (Pb) on the surface sediments in Sebou river estuary (Morocco) and evaluated the role of sediment grain size and organic carbon (OC) on the distribution of metals. Sixteen numbers of surface sediment samples collected during the summer period of 2019 from Sebou estuary were used for the study. The dominance of fine-grained sediments (clay and silt) was observed in the study region. The organic carbon distribution indicates that they were brought from the surroundings of coastal areas. Correlation analysis indicates that fine-grained particles and organic carbon (OC) control the distribution of metals and suggest strong association between metals and fine-grained fractions. Significant correlations were evident between Zn and Mn (r = 0.66), and between Mn and Fe (r = 0.70). The correlations between OC versus Mn (r = 0.80), OC and sand (r = −0.70), OC versus silt (r = 0.96), and OC and clay (r = 0.87) were significant. Contamination levels of metals were examined by using geo-accumulation index and contamination factor, which indicate that the estuarine sediments were unpolluted to moderately polluted with heavy metals. The study thus provides baseline data on the heavy metal distribution in the Sebou estuary for identifying the source of future contamination.

Dissolved oxygen (DO) concentration is an essential indicator for assessment of estuary ecosystems. According to our knowledge, there is no research on the depth profiles of the DO and associated water quality variables of the entire Bouregreg estuary (Morocco). Water samples were collected from three stations at 0.5-m depth intervals during high and low tides (10/11/2021, 20/03/2022, and 02/07/2022). Our study shows that the DO concentrations ranged between 5.5 and 11.8 mg/L and demonstrated an inconsistent stratification pattern. When the tide was high and low in most of the study area, the bottom layer had a higher concentration of DO than the surface layer. There was a relatively high concentration of DO in the bottom layer of the estuary and a relatively low concentration in the surface layer of the estuary due to a high rate of freshwater flow on the surface (the release of Sidi Mohammed Ben Abdellah dam and the existence of estuarine gravitational circulation). Salinity, pH, water temperature, and water transparency ranged from 19.4 to 35.8 ppt, 7.0 to 8.7, 17 to 23 °C, and 16 to 21 cm, respectively, considering the depth profiles in the study area. The study provides scientific support for ecology operation and considerable advances in understanding the ecosystem dynamics of the Bouregreg estuary.